Although patients with small lymphocytic lymphoma and chronic lymphocytic leukemia (SLL/CLL) have CD20 expression on malignant lymphocytes, response rates with standard rituximab (Rituxan) courses in refractory patients have been low. However, our initial experience with first-line therapy produced responses in 15 of 23 patients with SLL. We have therefore expanded our experience, and have now treated a total of 68 previously untreated patients with either SLL (37 patients) or CLL (31 patients) with single-agent rituximab.

All patients received rituximab (375 mg/m² weekly × 4); patients with objective response or stable disease at reevaluation (6 weeks) continued maintenance courses of rituximab, using a standard 4-week schedule, every 6 months for a maximum of four courses. Eligibility requirements included stage III or IV SLL or CLL, no previous therapy, Eastern Cooperative Oncology Group performance status of 0 to 2, no life-threatening signs/symptoms, and informed consent.

Between April 1998 and June 2001, 68 patients were treated in two sequential multicenter, community-based clinical trials; 66 have been evaluated for treatment response. Patient characteristics included median age, 66 years (range: 38-89 years); B symptoms, 13 patients (23%); white blood cell count ³ 50,000 cells/mL, 19 patients (28%). At week 6, 33 of 66 evaluable patients (50%) had objective responses (9% complete response rate), and 32 additional patients (48%) had stable disease. Twenty-seven patients remain on therapy and are receiving maintenance rituximab courses. Median follow-up of the initial 24 patients is 26 months; in these patients, median progression-free survival was 35 months. Toxicity with this treatment program was limited to the typical rituximab-related infusion reactions; only one patient had reversible grade 3/4 toxicity.

CONCLUSION: Rituximab is highly active as first-line therapy for CLL/SLL, producing substantially higher responses than have previously been seen in patients with refractory disease. Further follow-up is necessary to assess the duration of response and the benefit of maintenance treatment with rituximab. Data correlating the response rate with surface CD20 antigen density will also be presented. Rituximab should be evaluated as part of first-line combination therapy for patients with CLL/SLL.

Click here to read Dr. Bruce Cheson's commentary on this abstract.